The helicoil "repair" was patented in USA 1938 and was used on NEW aircraft engines for reinforcing threads, so no miserable repair ! The Böllhoff company got the licence for producing Helicoil in 1956 and is well known since for great thread repairs or reinforcements requiring minimal space around holes.
On Vincents you can be lucky to get one with acceptable threads all around. If not so then well, no question for me to do helicoils , metric certainly, for reasons. No desire for me to shop around for ancient silly British fasteners, taps, and helicoils for these or even doing the mysterious thread games like here each month or so. So in my cases you won´t find a lot of imperial stuff except for bigger threads like on gearbox shafts. Helicoils are quick repair or adaptation to metric and take higher loads from this act. You certainly lubricate threads when assembling with stainless bolts, don´t you as a good practise ?? Some don´t like stainless , reason is bolts were not lubricated before so seizures are the consequence. But this disease is not a single problem with stainless: Do same assembly with plane steel bolts into plain steel nuts, no lube applied, and I mean NO lube and no galvanized coats and you get exactly same seized threads. Or do same test with alu bolts in alu nuts - seizure guaranteed. Simple solution, grease your nuts and bolts or get the Loctite when assembling and you are fine ever after.
Vic